Vývoj standardu digitální mobilní sítě pro hlasovou komunikaci začal v první polovině 80. let minulého století společnostmi Nordic Telecom (severské státy využívající Nordic Mobile Telephony 450 MHz (NMT-450))a holandským Postal, Telegraph and Telephone (PTT) (národní regulátor). Evropská komise navrhla použití pásma 900 MHz a vydala nařízení pro vyhrazení tohoto pásma v jednotlivých státech pro zajištění roamingu. V roce 1987 byla založena skupina Group Speciale Mobile. Zahrnovala ...
26: Velikost datového rámce pro r˚uznˇe dlouhé pakety [internet]
Data Rates
. chose send five slot packets both
directions, the data rate would reduced 433.)
Bluetooth ACL packets can either Data Medium (DM) Data High
(DH) type.Systémy mobilních komunikací 166
Sestavení sítˇe
• Procedura Inguiry pro vyhledání ostatních zaˇrízení
• 3200 skok˚u, kanál˚u podle zvolené posloupnosti
• rozdˇelení ˇcásti kanálech, celková doba trvání
2 posloupnost[1 16] 256 2iterace 0.The application software should pre-
sent this transparently, but still worthwhile exercise understand the
complete procedures; they are covered the following sections.7 The Payload Bluetooth Packets
13/15 Data
1 Slot 1/3 Data
3 Slot 7/9 Data
5 Slot
Access Header Payload Guard
Obrázek 5.2 Kbps the single slot packets this asym-
metric link would carry 57.The inquiring device must trying discover neigh-
bouring devices, and the inquiry scanning device must willing discov-
ered (see Figure 1.This gives the maximum baseband data
rate single direction 723.6 Bluetooth Device Discovery
I in
inquiry scan mode
I in
inquiry scan mode
I in
inquiry mode
Inquiry
Inquiry response
Inquiry
Inquiry response
I see phone
and PDA
Obrázek 5.A DH5 packet which utilizes five slots can carry the max-
imum amount data: 339 bytes, 2712 bits.6 Kbps.The inquiring device
changes frequencies 3200 times second (twice the rate for device normal
connection). So, take account the
packet overheads already discussed, 2858 bits are transmitted over the air interface
for every 2712 bits data payload.
The inquiring device transmits series inquiry packets.The packets achieve higher data rate using less error correc-
tion the packet.These packets not identify the inquiring
device any way; they are packets containing inquiry access code which
inquiry scanning devices will recognize.7.This fast frequency hopping allows the inquirer cover range of
frequencies rapidly possible. 16-bit CRC also included every ACL
packet, but this not illustrated Figure 1.These short packets
are sent out rapidly sequence different frequencies.6). One way mitigate this limitation transmit for a
longer period time: slots.01s 10, 24s
• vyhledávající zaˇrízení výsílá dvou sobˇe jdoucích frekvencích ˇceká odezvu
• vyhledávající zaˇrízení mˇení frekvenci velmi rychle, vyhledávané mˇení frekvenci pomalu "brzy sejdou"
• Procedura Inquiry trvá 10,24s
20 Chapter Introducing Bluetooth Applications
Potentially, the user could simply select the option print, and the processes
of device discovery, service discovery, and connection could happen automatically
without further intervention from the user.
www.syngress.All the extra bandwidth used for payload
data with consequent improvement efficiency (illustrated Figure 1.com
Figure 1.25: Procedura Inquiry [internet]
Doba trvání stestavování sítˇe
Tabulka 5.8: Pˇrehled doby trvání jednotlivých procedur pˇri sestavování spojení
Procedura Minimum (s) Pr˚umˇer (s) Maximum
Inquiry 0,00125 3-5 10,24-30,72
Paging 0,0025 1,28 2,56
Celkem 0,00375 4,28-6,28 12,8 33,28
Payload
26 Chapter Introducing Bluetooth Applications
Within one slot packet these requirements leave only one-third the
bandwidth for the payload data—and this can only transmitted every other
slot, every 1250μs.7).Thus, five slot packet, the master will transmit f(k), and after the
five slots will transmit f(k+5).
Discovering Devices
Before any two devices can through device discovery, they must inquiry
and inquiry scan modes.9 Kbps!
The choice symmetric asymmetric links allows our user scenarios to
take account the improvement data rate one direction the asymmetric
link (for example, our PDA browsing the Web via server will require more
bandwidth while downloading pages than will require for specify the
Figure 1.
While transmitting over more than one slot, the devices remain the same fre-
quency, moving the next frequency the hopping sequence the end the
packet
